1. Field of the Invention
The present invention relates, in general, to a color filter substrate for a liquid crystal display (LCD) and a method of fabricating the same, and more particularly, to a color filter substrate for an LCD and a method of fabricating the same, that are capable of shielding an electrostatic field due to external static electricity and improving image display quality to increase high brightness characteristics and readability by forming a transparent conductive layer of a porous structure having a plurality of holes on a rear surface of an insulating substrate applied to the color filter substrate for an LCD.
2. Description of the Related Art
In recent times, one of LCDs which are widely used is a twisted nematic (TN) LCD. The TN LCD employs a method of forming electrodes on two substrates, respectively, arranging a liquid crystal director to be twisted 90°, and applying a voltage to the electrodes to drive the liquid crystal director.
However, the TN LCD has a disadvantage of providing a narrow viewing angle.
Therefore, in recent times, in order to solve the narrow viewing angle problem, research on LCDs employing various new modes has been widely performed, among which are, for example, an in-plane switching (IPS) mode, an optically compensated birefringence (OCB) mode, and so on.
Among the modes, an LCD employing the IPS mode involves forming two electrodes on a substrate to horizontally rotate liquid crystal molecules with respect to the substrate such that a voltage is applied between the two electrodes to generate an electric field in a direction parallel to the substrate. That is, a longitudinal axis of the liquid crystal molecules is not raised with respect to the substrate.
For this reason, a small variation in birefringence of liquid crystal with respect to a viewing direction causes better viewing angle characteristics in comparison with the conventional TN LCOD.
Hereinafter, a conventional LCD employing an IPS mode will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional view of a conventional LCD employing an IPS mode.
Referring to FIG. 1, a liquid crystal panel constituting the conventional LCD employing an IPS mode generally includes a color filter substrate 10 and a thin film transistor substrate (not shown), which are opposite to each other, and a liquid crystal layer (not shown) disposed between the two substrates.
Here, the color filter substrate 10 includes black matrices 12 disposed on an upper substrate 11 at predetermined intervals, color filters 13 disposed between the black matrices 12, and an overcoat layer 14 formed on the entire surface including the color filters 13.
Meanwhile, while not shown, the thin film transistor substrate generally includes data lines disposed opposite to the black matrices 12, counter electrodes formed at one sides of the data lines, and pixel electrodes formed at the other sides of the data lines, on a lower substrate.
In addition, the liquid crystal layer is interposed between the color filter substrate 10 and the thin film transistor substrate, and a transparent conductive layer 15 is formed on an outer surface of the upper substrate 11, i.e., a rear surface thereof, in order to shield static electricity applied from the exterior.
That is, when the substrate is in contact with a charged external object, the upper substrate 11 is also charged to exert direct influence on alignment of the liquid crystal molecules.
Influence due to the charged upper substrate 11 renders light transmittance unable to be controlled by a data voltage, thereby deteriorating image quality.
Therefore, in order to prevent deterioration of image quality due to the static electricity, the transparent conductive layer 15 may be formed on the rear surface of the upper substrate 11 to prevent static electricity from being applied from the exterior.
As described above, the conventional transparent conductive layer 15, formed on the rear surface of the upper substrate to remove static electricity, is in contact with a metal bezel of the LCD to function as a ground electrode and to prevent the color filter substrate 10 as a dielectric body from being charged upon introduction of static electricity from the exterior, thereby preventing an electric field introduced into the liquid crystal panel due to the static electricity.
In addition, when the electric field is introduced into the liquid crystal panel, liquid crystals in the liquid crystal panel of a normally black mode are driven by affection of the electric field so that a black screen cannot be driven.
However, the transparent conductive layer 15 formed on the rear surface of the upper substrate 11 to remove static electricity acts as a factor lowering transmissivity of the liquid crystal panel by 8% to 10%, thereby potentially disappointing a customer demanding high brightness.
In addition, the upper substrate 11 and the transparent conductive layer 15 have different refractive indexes to directly reflect external light such as sunlight or fluorescent light at an interface between the upper substrate 11 and the transparent conductive layer 15, not diffusing the external lighter thereby lowering a contrast ratio to deteriorate image display quality.